This invention pertains to the field of obstetrics. In the field of obstetrics, one of the most important problems is the management of preterm labor. A significant number of the pregnancies progressing past 20 weeks of gestation experience premature labor and delivery which is a leading cause of neonatal morbidity and mortality.
It has recently been proposed that a selective oxytocin antagonist would be the ideal tocolytic agent. In the last few years, evidence has accumulated to suggest strongly that oxytocin is the physiological initiator of labor in several mammalian species including humans. Oxytocin is believed to exert this effect in part by directly contracting the uterine myometrium and in part by enhancing the synthesis and release of contractile prostaglandins from the uterine endometrium/decidua. These prostaglandins may, in addition, be important in the cervical ripening process. By these mechanisms, the process of labor (term and preterm) is initiated by a heightened sensitivity of the uterus to oxytocin, resulting in part by a well-documented increase in the number of oxytocin receptors in this tissue. This `up-regulation` of oxytocin receptors and enhanced uterine sensitivity appears to be due to trophic effects of rising plasma levels of estrogen towards term. By blocking both the direct (contractile) and indirect (enhanced prostaglandin synthesis) effects of oxytocin on the uterus, a selective oxytocin antagonist would likely be more efficacious for treating preterm labor than current regimens. In addition, since oxytocin at term has major effects only on the uterus, such a compound would be expected to have few, if any, side effects.
The compounds of the present invention may also be useful for the treatment of dysmenorrhea. This condition is characterized by cyclic pain associated with menses during ovulatory cycles. The pain is thought to result from uterine contractions and ischemia, probably mediated by the effect of prostaglandins produced in the secretory endometrium. By blocking both the direct and indirect effects of oxytocin on the uterus, a selective oxytocin antagonist may be more efficacious for treating dysmenorrhea than current regimens.
An additional use for the present invention is for the stoppage of the labor preparatory to Caesarian delivery. Certain spiroindanylpiperidines and spiroindenylpiperidines are known (U.S. Pat. Nos. 3,654,287 and 3,666,764), however, they are reported to be useful as anesthetic agents which is quite distinct from the utility of the present invention.
It was, therefore, a purpose of this invention to identify substances which more effectively antagonize the function of oxytocin in disease states in animals, preferably mammals, especially in humans. It was another purpose of this invention to prepare novel compounds which more selectively inhibit oxytocin. It was still another purpose of this invention to develop a method of antagonizing the functions of oxytocin in disease states in mammals. It is also a purpose of this invention to develop a method of preventing or treating oxytocin related disorders of particularly preterm labor and dysmenorrhea.